Fix opts table damaging by CRUD methods

[AnaNek]

If we have opts variable and we pass it to some crud method
(upsert_object for example) and then use opts variable again
for crud method (get for example) we receive an error because
*_object method damages opts variable adding
add_space_schema_hash parameter to opts variable.

Closes #192

[ligurio]

Thanks for the patch!

[ligurio]

Why do you use eval() instead of call()?

    -- insert_object
    local result, err = g.cluster.main_server.net_box:call(
            'crud.insert_object', {
                'customers',
                {id = 1, name = 'Fedor', age = 59},
                insert_opts
            }
    )

[AnaNek]

If I would use call() I could not catch modification of opts table

[olegrok]

Thanks for your patch. See my two suggestions.

[mRrvz]

It seems to me that the word create is more suitable here (not make), or get

[AnaNek]

make_option name is often used for parsing options (in Python modules for example). Thats why it seems to me that this name is suitable.

[Totktonada]

A bit more bikeshedding: it looks specific for the add_space_schema_hash option, so it would be better either choose a specific name or rewrite the function to be common:

-- Merge two options map.
--
-- `a` and/or `b` can be `nil`.
--
-- If `a.foo` and `b.foo` exists, prefer `b.foo`.
function utils.merge_options(a, b)
    return fun.chain(a or {}, b or {}):tomap()
end

So the call will be the following:

-opts = utils.make_options(opts, true)
+opts = utils.merge_options(opts, {add_space_schema_hash = true})

Maybe a bit more Lua tables, but the call becomes more readable (now we see what is the true/false value).

[AnaNek]

Updated:

+-- Merge two options map.
+--
+-- `opts_a` and/or `opts_b` can be `nil`.
+--
+-- If `opts_a.foo` and `opts_b.foo` exists, prefer `opts_b.foo`.
+function utils.merge_options(opts_a, opts_b)
+    return fun.chain(opts_a or {}, opts_b or {}):tomap()
+end

[Totktonada]

LGTM (but there is a nitpicking around naming, see below).